Telephone system.



E. E. H|NRICHSEN. TELEPHONE SYSTEM.

APPLICATION FILED 00TH]. I915.

Patented Nov. 21, 1916.

4 SHEETSSHEET I- Fig.

F r- 4/ 42 T I III- LL HWIIH" Ell ' H //7ve/if0/ Edward 5 hflvr/c/rsen.

E. E; HINRICHSEN.

TELEPHONE 'SYSTEM.

A'PPLICATION FILED 0618, I9l5.

N d aw m av ln v n for: Edward E. Hi/vrichsen. y

-A rry.

E. E. HINRICHSEN.

TELEPHONE SYSTEM,

APPLICATION FILED OCT. 8. 1915.

Patnted Nov. 21, 191

I /nven/or: Edward E. H/hk/k'hsen E.- E. HINRICHSE N. TELEPHONE SYSTEM.

APPLICATION! FILED OCT. 31 -1915.

Patented Nov. "21, 1916.

4 SHEETS-SHEET 4.

UNITED STATES] PATENT QFFIGE.

EDWARD E. HINRICHSEN, OF EAST ORANGE, NEW JERSEY, ASSIGNOB, BY MESNEASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPO- RATIONNEW YORK.

Specification of Letters Patent.

TELEPHONE I SYSTEM.

Patented Nov. 21, 1916.

I To all/whom it may concern:

Be it known that I, EDWARD E. HINnnn-r son, a citizen of the UnitedStates res ding at East Orange, in the county of Esscx'and State of NewJersey, have invented new and useful Improvements in'Telephonc Systems,of which tlie following is a full, clear, concise, and exactdescription.

This invention relates to telephone systems, and more particularly tosuch systems of the type wherein, in establishing connections betweensubscribers, three or more centrail and local ofilces are involved.

The object of this invention is to provide atelephone system in whichconnections may be established from one subscribefsline through twocentral offices and one of aplurality of local oflices to anothersubscribers line without the intervention of an operator at one of thecentral ofiices and with-the use of a minimum amount of apparatus. r s

In accordance with gehis invention, there is provided amain trunkcircuit extending from a. first to a second central oiiicc, andlocaltrunk circuits and flSSOllllltBtlCflll wire circuits, one of eachextending); from the sccoml central -"pllice-to each of a plurality oflocal ollices."" At: the second central oflice there is astep-by-stepselecting device as sociated with thcinain trunk circuit andcontrolled thercovcr from an impulse transmitter associated with a linkcircuit connect- ,cd with the main trunk circuitat the first central.ollice, to select a local trunk circuit extending to one of the localoflices and tluii'eai'tcr to control the connection of the main trunkcircuit with an assoeihted call wire circuit of the selected loca'bl'llllk circuit. r

This invention is an improvement over that disclosed and claimed in anapplication Serial No. 54,336, filed October (3, 19.15, by me.improvement over that disclosed and claimed in. application Serial No.54:.336, in that the present inventionprovides for a. greatly increasednumber of ofiices local to the second.

central oiiices, any one of which may be selected from the first centralofli'ce. The

present mventlon also accomplishes this re- The present invention is adecidedstoodby reference to the accompanying drawings illustrating oneembodiment there: of. To obtain a clear idea of the entire system, thefigures should be placed side by side in the following order" from leftto right,-1, 2, 3, 4.

As shown in the drawings, this invention comprises a main trunk circuit13, the outgoingend of which is located at a first or originatingcentral oilice X, and the incoming end of which terminates in a secondcentral office Y. Located at central ofiice X is acord circuit A used tocomplete connections from an originating subscriber (not shown), to theincoming end of the main trunk circuit B. Extending; from the secondcentral. office Y to local oflices E, F, G and H are local trunkcircuits G and 'asso ciated call Wire circuits I), there being one localtrunk circuit C and an associated call' wire circuit D for each localoffice. The cord circuit A, shown in-Figure 1, and the outgoing! end ofthe main trunk circuit 13, shown 1n log. 2, are located at the firstcenlral oflice X, while the incoming end of the main trunk circuit B,shown in Fig. and

to the left of the dotted line in Fig. 1, is located at the secondcentral oilice Y. The incoming end of the local trunk circuit C, shownbetween the dotted lines in Fig. 4:, is located at the local office F.Only one .(.'.o1n}' lcte local trunk circuit C and its assame that shownfor the same circuits extending to localofiice'F.

- At the central ollicc X, there located an impulse transmitter 36(shown within the. dotted lines). This transmitter 36is common toanoperators position and comprises a starting relay 44, an interrupter, a5k:- lecting key for each local oflice, and a pair of relays for eachlocal ofiice, The intersuch as to permit of the proper operationofselecting apparatus in the main trunk circuit B. Selecting keys 40, 41,42 and 43 correspond effectively to the local oflices F, G and Key 40controls relays 47 and 48; key 41 controls these two relays and relays49 and 50; key 42 controls these four relays and relays 51 and 52; andkey 43 controls these six relays and relays 53 and 54. Oneshort and onelong impulse is sent out by the transmitter 36 when key is actuated, twoshort pnd one long impulse when key 41 is actuated, three short and onelong impulse by the actuation of key 42, and four short and one longimpulse by the actuation of key 43. Should it be de sired to equip theimpulse transmitter 36 for selecting more than four local oflices, thereshould be added to the equipment shown, one key and two relays (similarto any pair 47 and 48 or 49 and 50, etc.) for each additional localoflice.-

At the second central oliice Y there 1s located a ,step-by-step selector(shown within the dotted line) controlled from the impulse transmitter36. This selector 60 comprises an operating or stepping magnet 28 havingan armature 61 operating a stepping pawl 62. Each time that steppingmagnet 28 is energized, stepping pawl 62 engages a ratchet wheel 63-toadvance one step a contact arin or wiper 64 rotatablewith the ratchetwheel 63. A holding pawl 65 normally engages the ratchet wheel 63 tohold wiper 64 in advanced position, The holdingpawl 65 is controlled bya release magnet 30 which, upon being energized, causes thedisengagement of the holding pawl and the ratchet wheel, whereupon theratchet wheel, due to the action of a spiral spring 68, returns thewiper 64 to normal position, as shown in the drawing. The selector hastwo oil-normal contacts 67 and67 and four contacts to which areconnected conductors extending to the windings of relays and 56, whichcontrol the connectiop of the main trunk circuit B to the local trunkand associated call wire circuits extending respec tively to the localoiiices E, F, G and H. The selector, obviously, may be equipped -\\'ithadditional contacts to care for as many ,pwticular conditions may i 65warrant.

local ollices as Assuming that the operator at the first central oflicehas received a call for a subscriber whose line terminates in localoffice F, the operator will insert calling plug 6 into jack 7 of themain trunk circuit B, thereby energizing relay 15 over a circuit frombattery through the winding of relay 38, sleeve contacts of plug andJack, both windings of relay 15, and the normal contact of relay 16 toground. Relay.15, in operating, causes the actuation of relay 17, whichconnects the talking strands of the main trunk circuit B through to thetip and ring contacts of the jack 7 and opens the circuit of relay 16 atthe normal contact of relay 15, thereby preventing the connection of asecond cord circuit to the main trunk circuit B during the connectiontherewith of cord circuit A. The operation of relay 15 also causes theoperation of relay 18 over a circuit from battery through the contact ofrelay 27, left-hand winding of relay 18 and alternate contact of relay15 to ground. The operation of relay 18 causes the operation of relays22 and 25 over a circuit from nega tive signaling battery throughcontact of relay 18, windings of relays 22 and 23, retardation coil 58,ring conductor of main trunk circuit 13, retardation coil 59, windingsof relays 24 and 25, and resistance 73 to ground. Relay 23 is marginaland does not operate when included in circuit with both windings ofrelay 25 and resistance 73, but does operate when the right-hand windingof relay 25 and resistance 73 is removed from the circuit. Relay 22 inoperating removes the short circuit from the left-hand winding of relay27. This winding is of high resistance, while the right-hand wind ing isof low resistance. Relay 24 is polar ized, so that it does not operateon negative signaling battery; hence it does not 'operate when the plug6 is first inserted in the jack 7, thereby preventing the operation ofthe operating or stepping magnet 28 of the selector 60. The operation ofrelay 25 causes the operation of relay 26. The operator at centraloffice X may-now actuate listening key 39 and selectingkey 41. Theactuation of these two keys causes the operation of relay 2'? over acircuit from battery through the winding of starting relay 44, lowercontact of key 41, upper contact of listening key 39, tip conductors ofthe cord circuit A 30 .eration oi 'the rollers 53.

are in constant mesh with a bevel-gear 15 on a shaft 46 journaled in abracket 47 of the frame and having at its rearward end a fixedbevel-gear 48 that n'ieshes \vith betelgear 49 fast on the shaft (latch42 is provided with a handle H, and may be called the spool drit'e andshift mechanism. By'the mechanlsin described, t'h'espool may be carriedtransversely around the man- 1 (1rd, laying the tape or strip spirallyor otherwise whilev the mandrel is rotated. Preferably, for the purposenou' pi'u-tieularly intended, the spool is canted, as shown. so that thetape or strip is led to the mandrel at an angle, asshown in Fig. 3,whereby spiral winding is facilitated. \Vhen a suiticient number ofreverse-spiral windings 50 and 51 have been laid on the mandrel to forma foundation tube for the clencher head strips 52, straight pieces ofvulcaniz able rubber of proper crosssectional contour are put.- betweenthe rollers 53 and the side of the foundatioi'i, and then rolled intoplace.

as rings adherent to the tubular, annular foundation formed by reverselywinding the speet of the mandrel or spool-carrier, and r s 111anycvcntthe tape or strip of frictional material lH,'Qtllltlgl]lKltHtension' at alletages' of buildi g gap the carcass.

,- When the clenehrr have been laid or rolled inplace, further 0reverse-spiral wiruling's 54 a1ul55 (as many alternating, overlappingstrips-as desircd,-)

a.re"put i1'1 place; the roller. 53 being thrown out of use or intoidle' .msition, as shown in Fig. 1. In Fi i. 5 the-"are shown in workingposition. 'Each is loosely mounted on a journal 56 l'iinged at to asuitable bracket 58 and held up to their Work by a spring 59 that isdetachable, so that instead of pulling the journals 56 toward oneanother and the interi'nediate portion of the mandrel, the. journals mayfall away from eagli other into idle position. v

The peripl'ieral work surfaces of the roll-. ers-itl have a shape thatcorres 'ionds to the exterior wall- (of the vulcanizahle rubber headstrip) that lies -bet.- \\'een ils upper or grooved. edge and its inneredge, and vdoes not-engage the outer.peripheral wall; that is, the wall,otthe groove of the bez'ul-toru'ling strip. As these strips arepre-hn'i'rnal.

with continuous gri'a'nes-along their outer peripheral edges, itisnnportantnot to tieand it also do able that the rollers 53 should beheld. up 'totheirwork elastically, slbet'oredcscribed method and by useot the Each beadbeaul-iorniine stripsas by spring 59, in order tominimize the deformation due to the pressure of the rollers on thepre'formed bead-strips.-

When the carcass has been built up, it'is initially in the form of anannular tube with clencher bead rings between the foundation and outerplies. To convert this tube into shoe-fornnit is cut around its innerperiphery, as by a rotary cutter 59, the mandrel havlng an lnnerperipheral slit ()0 to permit this operation. The mandrel is preferablyof knock-down or collapsible type, comprising segments '01, m and m andfasteners m, to permit removal of the shoes at the proper time. Aftertrimming and working .the edges of the peripherallyslit tube intoshapeto shape/the margin's'of theouter plies to the foundation andbeadrings, or before so doing, the usual rubber, ,a'nnulartread l willlbestretched in place around'the outer periphery'of the carcass;and'thereafter the whole may be cured in molds, or be wrapped by .thepresent machine prelin'iinary to vulcanization. It will be observed thatthe spool is carried positively by its carrier.

'Thisis desirable for thebest results, be cause the tapes or stripsare'thereby pulled tightly in place around tl1e-1nandrel,tightly uponone another, so as to make the carcass very compact.

If desired, annular bead-supporting rings 61 may be used to hold' thebead rings in place, these rings to ,be removed at'ter the initiallyformed, annular tube is slit around its inner circumference. In practicewe find these bead rings im 'iorta-nt because'if they are not used, thebeatl-forn'iingstrips' 52 pt unyulcanized rubber'ar'e-apt to be deformedby tho coinprt on to which 't-hey 'are. in such case, subjected by thestrain of the supplementaryor outer; windings. The two rings Glarechan'lfered and. slightly held apart ,(by thefbeads 52) at-th'eiropposed inner edges, at (32, oppositotheinner peripheralcutter-receivingslit 60 of the. collapsible mandrel, so that the cutter59 can pass first through theouter winding, or shell, then betweenthe'op 'iosed;edges of the bead rings ('11, and then through the inner\vind-' ing into the slit (30, which ailords a elearance for the cutter;The rings 52 are. made ofrelativcly thin stock, and ought to be, asshown, of uniform thickness throughout their annular andcross-situational extent; so as 'not to involre the use of unur essm'ymaterial. Their interior surfaces'should be "laterally curving, assl'iown, so as to permit.

'ii'in'er periphery of the shoe while the-ei- I terror strips are, being\vound-: 1 n place.- Ltornn-them when. they are rolled inplace; j

'e find, in practice, that, inmany sires o't shoes made 111 accordancewith the herein contact and wiper 64 of the selector 60, lefthandwinding of relay 57, and contact 01:: relay 29 to ground. Belay 57, inoperating, completes a locking circuit for relays 55, 56 and 57 throughthe ri ht-hand winding of relay 57 and contact tlereof, and left-handcontact of relay 26 to ground. The operation of relays 55 and 56 extendsthe main trunk circuit 13 through to the armatures of relay 70. Relay 56also closes its contact 74, 'causingthe operation of relays 75 and 76,the operation of the latter causing the lighting of lam 77 before'theoperator at the'local oili'ce The operation of relay 75 short-circuitsthe righthand winding of ,relay 25 and resistance 73, whereupon marginalrelay 23 operates, short-circuiting the right-hand winding of relay 1'5,causing the operation of relay 38, thereby lighting the supervisory lamp37.

If the call wire circuit extending to local ofiice F is not busy, theclosure of contact 66 of relay 55 causes the operation of relay 70 overa circuit from battery through the contact and left-hand winding ofrelay 71, contact 66 of relay 5'5, winding of relay 70, and winding ofrelay 72 to ground. Relay 70 in operating, completes the connection ofthe main trunk circuit B to the call wire circuit extending from thesecond central ofiice to local oifice F. Relay 70 in operating alsocloses its contact 69, which shortcircuits relay 72, preventingthe'operation thereof. Relay 71 is marginal and does not operate whenincluded in circuit with the windings of relays 70 and 72, but doesopcrate when included in circuit with the winding of relay (0 only, sothat when the 'winding of relay 72 is short-circuited by the closure ofcontact 69 of relay 70, relay 71 operates. The operator at the centralofiice X may now communicate to the operator at local office F thenumber of the line to'which connection is desired.

The operator at local oflice F, after being advised of the numberof thedesired line, inserts the plu of the local trunk circuit-G into the jack0 the desired subscribers line, whereupon relay 7 8 operates,extinguishingsth lamp 77. The cutoli relay of the su cribers line' isalso operated. The operator at the central oflice X may now releaseselectin key 41, thereby releasing reincluded in circuit with the highresistance winding only of relay 57. Since relay 55 is marginal, itreleases when included 1n circuit with only the high resistance windingof relay 57 and relay 56. Relay 55, in n releasing, disconnects the maintrunk circuit B from the call wire circuit 1) and con nects it with thelocal trunk circuit G ex tending to the local office F. Bela 55 inreleasing, also causes the release 0 relays and .71 which restores thecall wire circuit D to its normal condition. The operator at the centraloffice X now restores listening key 39 to its original position andactuates ringing key to connect a source of ringing currcnt 81 to therin side and ground to the tip side of the calling and of the cordcircuit A, whereupon relay 82 is actuated, causing the operation ofrelays 83 and 84. Relay 83, in opcratin connects the tip and ringconductors o the main trunk circuit B to the secondar of a transformer85, the primary of which has been included in closed circuit with asource of alternating current 86 and interrupter 99 by the operation ofrelay 84. Hi h frequency current from the secondary o transformer passesthrough re eating coil 87 and operates relay 88. Be ay 89 is noi-- mallyenergized, so,.when relay 88 operates relay 89 releases, causin theoperation 0 relay 90. Relay 89 is s ow in releasin so that it will notrelease and cause false rings should relay 88 be energized momentarilydue to disturbances on the trunk. Relay 90, in' operating, connects asource of ringing current 91 through the local trunk circuit (J, causingthe operation of relay 92, whereupon relay 93 is energized connecting asource of ringin current 94 at the local ofiice F to the cafied line.Ringing current remains connected to the called line only as long as theoperator at central office X keeps ringing key 80 operated.

In response to the operation of the call hell at the subscribersstation, the subscriber removes the receiver from the switchhook,causing the operation of supervisory relay 95, w luch removes the shortcircuit of resistance 96, whereupon rela- 75 I receives a reduced flowof current an mleases. The release of relay 7 5 removes the shortcircuit from the ri hthand winding of relay 25 and resistance 73,thegeby reducing the amount of current through relay 23 causing therelease thereof. Relay 25 remains operated. Relay 23, in releasing,causes the release of relay 38, thereby extinguishing the supervisorylamp 37.

.At the termination of the conversation when the receiver at the calledstation is restored to the switchhook, relay 38 isagain energized,relighting supervisory lamp,37, which serves. as a disconnect si :1 tothe operator at central ofiioe X. T a -operator indicates to nowwithdraws the plug 6 from the jack 7,

whereupon relays 15, 17 and 18 release. The

thereby released. The release of relay causes the release-of relay 76,whereupon supervisory lamp 77 lights to furnish a disconnect signal tothe operator at the local ofilce F, who then withdraws the plug of thelocal trunk from the jack of the line, restorto normal.

ing all of the apparatus D from the central The' call wire circuits.oiiiceY to the local offices E, F, G and H are used in handlingconnections originating in the central ofiice Y and may be multiplcdthrough the difierent 100 represents-a call operators" positions. wirekey at one such operators position. Actuation of key 100, if the callwire circuit is not busy, causes the actuation of relay 101 over acircuit from battery through the contact and left-hand winding of relay71, lower contact of key 100, winding of relays 101 and 102 to ground.Relay 102 does not operate'because relay 101 in operating closes itslower alternate contact 103, short-circuiting relay 102 and causing theoperation of relay 71. The operation of rela'y-lOl-also connects theoperators telephone set at the central oflice Y to the call wire circuitD extending to the local oflicell. Relay 71, in operating, re-.

moves the normal short circuit of the righthand winding thereof, therebyincluding both windings in circuit. Should this call wire circuit havebeen busy when the operator at the central office Y actuated key 100,

both windings of relay 71 would have been in circuit, thereby preventingthe operation of relay 101. Relay 102 would, however, have operated,lighting the lam 104 and operating relay 105. Y The lighting of the lamp104 indicates to the operator that the call wire circuit is in use, andthe operation of relay 105 connects a tone tothe receiver of thepperators telephone set, which also the operator that the call wirecircuit is in use.

Should the call wire circuit D extending to the local office F have beenbusy when the operator at central office X actuated listcning key 30 andselecting key 41 to select local oliice F, the prior: operation of relay7!. would have prevented. the operation. of relay 70, but relay 72wouldv have operated. Relay 72 operating,

tone to the normal contacts 106 and 116 of relay 70, whereby a tonewould have been lighting would have connected it.

transmitted to the receiver of the operators telephone set at thecentral office X, indicatmg to this operator that the call wire'circuitD extending to the local ofiice F was in use.

Suppose that, while a connection is set up through the central offices Xand Y and the local oflice F to a subscribers stationof this localoflice, the operator at central ol'lice X should receive another callfor connection to a subscribers line terminating in one of the localollices E, F, G or H, which second con-1 nection w0u ld necessitate theuse of the main trunk circuit B, the operator would insert a calhng plugof a second call circuit A into paratus associated with the main trunkcircult B is operated by the insertion of a callmg plug of-a second.cord c 1rcu1t into the jack 107 of a main trunk circuit B. No ap jack107 while another calling plug is connected to the jack 7, fortheenergizing cir-.

cult of relay 16 is open at a" contact of relay 15. As soon as theoperator at the central office X receiv'es the disconnect signal by theof supervisory lamp 37 in the cord circuit A connected to jack 7, thecalling plug 6 is withdrawn from the jack 7 Rela 1'5 releases, causingthelrelease of relays 1 and 18 and the. operation of relay 16. Theoperation of relay 16 causes the operation of relay 117 'to connect thetip and ring -'con-' ductors of the main. trunk circuitB to the tip andring contacts of the jack 107. Re- ,lay 16 in operating, also causes theoperation of relay 18. Relay .18 had, however, released before itscircuit was again completed by the actuation of relay 16. The momentaryrelease of relay 18 due to the release of relay 15, before itsopo'ra-tiondue to the operation of relay 16, causes the momentaryrelease of relay 25, which in turn causes the operation of the releasemagnet-30 to withdraw the holding pawl 65 from the ratchet wheel so thatthe wiper 64 returns to normal position. Upon the return of the wiper 64to normal, relays 56, 57, 75 and 76 are released. The release of relay 75 causes the lighting of lamp 77 to furnish a disconnect signal tov theoperator-at the local oiiice F, who then withdraws the plug from thejack. The operation of relay 18, due to the operation ofrelny'16,'causes the operation of relays 22 and 25, as-hereinbeforeexplained. The operator at central oiiice'X may then actuate listeningkey 39 and one of the keys of the impulse transmitter 36 to select thedesired local office. I

, After having communicated to the operj 'ator et the selected local"oliice the number of the desired subscribers line,-and after havingreleased the selecting key, the operator at the first central oilice mayfind t the wrong number has been transmitted to,

the operator at the localoflice, that the wrong local office has beenselected, that the right local oflice has been selected but that theoperator thereat has connected the local trunk circuit to the wrongsubscribers line, or the right subscribers line may have been connectedwith but the subscriber did not respond; In such cases, it, is desirablethat the first central oflice operator may be able to communicate withthe operator at the desired local office without having to withdrawtheplug of the cord circuit from the jack of the main trunk circuit B. Thisis especially desirable for the reason that a second cord circuit may beconnected with the second jack of the main trunk circuit.

The present invention provides for the contingencies above mentioned.Assuming, for example, that the proper local otlice has been selectedand that the operator thcreat has connected the incoming end of thelocal trunk circuit C to the wrong suhscrihers line, and assumingfurther that the oliice selectedis local oflice F, the operator at thecentral ollice X may actuate listening key 39, and selecting key 41,which causes the actuation of relay 27 over a circuit from hatterthrough the winding of relay 44, lower con tact of key 41, upper contactof listening key 39,- tip conductors of the cord'circuit A and the maintrunk circuit B, and both windings of relay 27 to ground. The operationof relay 3? releases relay 18, which releases relays 22 and 25, therelease of relay 22 short'circuiting the high resistance winding ofrelay 27, causing the operation of starting relay H of the impulsetransmitter 36. The release of, relay releases relay 26, but, as beforeexplained, since relay 26 is slow in releasing, a circuit is completedfor the release magnet 30 of the selector 60, whereupon the holding pawlG5 is withdrawn from the ratchet Wheel 63 permitting wiper (H to returnto normal position, whereupon relays and 57 release. Thereafter thelocal trunk circuit from the cenfrom the lir'stHeentral ollice to selectone of' tral ollice Y to the local oilice F is selected in the mannerln-relnhefore described, and the mam trunk circuit B is connected to thecall wire circuit I) extending to the mice ator's telephone set at localollice F. The operator at central ollicc X ma)" then reinst-ruct theoperator at local office F as to the connection desired.

What is rlainied is: p

1; In a telephone system, a main trunk rim-nitextending from a first toa second egntral,ollire, local trunk circuits and associat-edcall wire-rn'cu1t s, one of each extending i'rom the second central oflice toeach .of a pluralitarof "localollices, a step-bystep selector atthmsccond ccntral'oilice controlled said local trunlrpircpits, andapparatus operconnect the main with the call wire circuit associatedwith the selected local trunk circuit.

2. In a telephone system, a main trunk circuit extending from a first toa second central oliice, local trunk circuits and associated call wirecircuits, one of each extending from the second central otlice'to eachof a plurality of local offices, a stepbj step selector at the secondcentral ofiice controlled from the first central ofiiceover said maintrunk circuit to select one of said local trunk circuits, and relaysoperating upon the selection of a local trunk circuit to wire circuitassociated with the selected local trunk circuit. v

3. In a telephone system, a main trunk circuit extending from a first toa second central ofiiee. local trunk circuits and associated call wirecircuits, one of each extend. ing from the second central oiiice to eachof a plurality of local oiiices, an impulse transmitter at the firstcentralolfice, a step by-step selector at the second central oiliceresponsive to impulses from said impulse transmitter transmitted oversaidmain trunk circuit to select one of said local: trunk circuits,

and apparatus operating upon the selection of a local trunkcircuit toconnect; said main trunk circuit with-the call a trunk circuit with thecall wire circuitasso ciated with the selected'localtrunk circuit;

4. In a telephone system,a main trunk circuit extending v centraloilice, local trunk circuits and assouiated call irire circuits, one ofeach extending from the second central office to each. of a plurality oflocal oliices', an impulse transmitter at the first central office, asource of from a. first to a second v signaling current thereat, arelay-associated I with the main trunk circuit at the first centraloilice responsive to current impulses from the-impulse transmitter tointermittently connect said sourceof signaling current with-the maintrunk circuit, astep bystep selector at the 'secoiid centralofiice-responsire to slgnaling'eurre'nt impulses over the main trunkcn'cuitto-select one of said local trunk circuits, andapparatusoperating upon the selection'ofa local trunk circuit to connect saidrnaintrunk-circuit, with the call wire circuit associated-with theselected local trunk circuit. v

5. In a telephone system, a main trunk circuit extending from a first toa second central otiicc, local trunk circuits and associated rall wirecircuits, one. ofeach extending from asecond central oflice to each of aplura'lity of local oflices, alink circuit, an im-.

pulse transmitter and-a source'of signaling current at the first centralofiice, a relay associated with the main trunkgcircuitat the firstcentral ofiice responsive 'tocurrent impulses from said --impulsetransmitter when said link circuit isconnected with said to signalingcurrent impulses over the main my numc this (3th clay of October, A. D.,

main trunk circuit, said relay intermittently .ncct said main trunkcircuit with the call connecting saicl'sourcc of signaling currentwirccircuit associated with the selected 2! to the main trunk circuit, aste1 -by-step selocal trunk circuit.

lcct-or at the second central office responsive In witness whereof Ihereunto subs'cribe trunk circuit 'to'sclect one of said local 1915.trunk circuits, and relays-opcruting upon the selection. ofu local trunkcircuit to con- EDl-R'Ul-l) 1*. HINRICHSEN.

